The invention relates to directional boring and, in particular to a system for boring through both soil and solid rock using the same machine.
At present, when underground utilities such as natural gas, potable water, or sanitary sewer pipes are placed in rock, trenches are excavated using large hard rock trenching equipment such as the Vermeer T-655, or possibly even shot using explosives. In these conditions, electric, telephone and cable TV lines are normally strung overhead along poles, mostly due to the difficulty and expense of placing them underground. Thus, in many situations, a solid rock formation will cause utility lines to be located above ground due to the difficulty of underground installation. Many such sites involve mixed conditions involving both a solid rock formation for part of the run and soil for the remainder, often at the beginning and end of the run. In such a situation, rock drilling or trenching equipment may lack the capability to bore through the soil to reach the rock formation.
Directional boring apparatus for making holes through soil are well known. The directional borer generally includes a series of drill rods joined end to end to form a drill string. The drill string is pushed or pulled through the soil by means of a powerful hydraulic device such as a hydraulic cylinder. See Malzahn, U.S. Pat. Nos. 4,945,999 and 5,070,848, and Cherrington, U.S. Pat. No. 4,697,775 (RE No. 33,793). The drill string may be pushed and rotated at the same time as described in Dunn, U.S. Pat. No. 4,953,633 and Deken, et al., U.S. Pat. No. 5,242,026. A spade, bit or head configured for boring is disposed at the end of the drill string and may include an ejection nozzle for water to assist in boring.
In one variation of the traditional boring system, a series of drill string rods are used in combination with a percussion tool mounted at the end of the series of rods. The rods can supply a steady pushing force to the impact and the interior of the rods can be used to supply the pneumatic borer with compressed air. See McDonald et al. U.S. Pat. No. 4,694,913. This system has, however, found limited application commercially, perhaps because the drill string tends to buckle when used for pushing if the bore hole is substantially wider than the diameter of the drill string.
Accurate directional boring necessarily requires information regarding the orientation and depth of a cutting or boring tool, which almost inevitably requires that a sensor and transmitting device (xe2x80x9csondexe2x80x9d) be attached to the cutting tool to prevent mis-boring and re-boring. One such device is described in U.S. Pat. No. 5,633,589, the disclosure of which is incorporated herein for all purposes. Baker U.S. Pat. No. 4,867,255 illustrates a steerable directional boring tool utilizing a pneumatic impactor.
Directional boring tools with rock drilling capability are described in Runquist U.S. Pat. No. 5,778,991 and in Cox European Patent Applications Nos. EP 857 852 A2 and EP 857 853 A2. However, although directional boring tools for both rock drilling and soil penetration are known, no prior art device has provided these capabilities in a single machine together with the ability to steer the tool in both soil and rock. The present invention addresses this need.
There is also a need in the art for a directional boring tool for rock drilling and soil penetration that provides a percussion hammer driven by liquid fluids, provides indexing of a device for detecting angular rotation (e.g., a sonde) and provides a method for ON/OFF control of the percussion hammer (e.g., pneumatic or liquid driven). In addition, there is a need for an apparatus that provides improved steerability of the drill head.
A drill head for an apparatus for directional boring according to the invention includes a holder (or housing) for a device for detecting angular orientation such as a sonde, a pneumatic hammer and a rotary bit assembly connected head to tail with the angular orientation housing at one end and the bit at the other. The drill head may also include a starter rod, which may be connected to the angular orientation detector housing. The bit preferably has a frontwardly facing main cutting surface with a plurality of cutting teeth disposed thereon and a gage tower radially outwardly offset from the main cutting surface having at least one frontwardly facing gage cutting tooth thereon suitable for cutting over an angle defined by less than a full rotation of the bit. The device for detecting angular orientation is in a predetermined alignment with the gage tower so that it determines the orientation of the gage tower relative to the axis of rotation of the drill head. In one preferred embodiment, the main cutting surface is substantially flat and circular and has a series of fluid ejection ports thereon, and the drill head has passages for conducting a drill fluid therethrough to the ejection ports. In another preferred embodiment, the bit has a heel portion on an outer side surface thereof at a position opposite the gage tower, which heel portion slopes inwardly from back to front.
Such a drill head may be used in a method for directional boring according to the invention using a directional boring machine which can push and rotate a drill string having the drill head mounted thereon. Such a method comprises the steps of boring straight through a medium by pushing and rotating the drill head with the drill string while delivering impacts to the bit with the hammer, prior to changing the boring direction, determining the angular orientation of the gage tower using the device for detecting angular orientation, and changing direction during boring by pushing and rotating the bit repeatedly over an angle defined by less than a full rotation of the bit while delivering impacts to the bit with the hammer, so that the drill head deviates in the direction of the cutting action of the gage tower. The medium may be soil, solid rock, or both at different times during the bore. In particular, the steps of boring straight and changing direction can be carried out in both soil and rock during the same boring run using the same bit.
According to a further aspect of the invention, a method is provided for directional boring in mixed conditions including both soil and solid rock. Such a method comprises the steps of boring straight in both soil and rock by pushing and rotating the drill head with the drill string while delivering impacts to the bit with the hammer, prior to changing the boring direction in both soil and rock, determining the angular orientation of the gage tower using the device for detecting angular orientation, changing direction when boring in rock by pushing and rotating the bit repeatedly over an angle defined by less than a full rotation of the bit while delivering impacts to the bit with the hammer, so that the drill head deviates in the direction of the cutting action of the gage tower, and changing direction when boring in soil by pushing the bit with the drill string without rotating it so that the drill head deviates in a direction of the gage tower and away from the heel portion. Since the main cutting face of the drill bit is large and flat, the pushing force of the drill string alone may be insufficient to steer the tool in soft ground without rotation. It is thus preferred to deliver impacts to the bit with the hammer while changing direction in soil. This method of the invention may provide better steering in some ground conditions.
Another aspect of the invention provides a drill head for an apparatus for horizontal directional drilling, comprising: a device for detecting angular orientation; a holder for the device for detecting angular orientation, the device for detecting angular orientation being disposed therein; a hammer driven by a liquid, the hammer arranged and configured to generate percussive blows; and a rotary bit assembly connected to the hammer, the rotary bit assembly arranged and configured for receiving the percussive blows, and wherein the rotary bit assembly is oriented through use of the device for detecting angular orientation to steer the drill head.
Still another aspect of the invention provides an apparatus for use in horizontal directional drilling in compressible soil, of the type having a drill string coupled to a directional boring machine at a proximal end and a drill head coupled to the drill string at a distal end of the drill string, comprising: a drill bit generally adapted and configured to bore through rock; a device for determining the angular orientation of the drill bit and for providing a generated signal corresponding to the orientation; and an offset coupling member attached at a first end to the drill string and at a second end to the drill bit, the member being offset from the longitudinal axis of the drill string, wherein, the offset member is oriented in response to the generated signals to steer the drill bit.
Still a further aspect of the invention provides a method for boring a hole through rock using a horizontal drilling apparatus and steering a drill head of the drilling apparatus, comprising: pushing the drill head, the drill head located at a front end of a drill string, through a medium; delivering impacts to a drill bit located at a distal end of the drill head with a hammer driven by a liquid, wherein the drill bit includes an effective steering geometry suitable for steering the drill head; periodically determining the angular orientation of the drill bit using a device for detecting angular orientation disposed on the drill head; and steering the drill head by pushing and rotating the drill bit repeatedly over an angle defined by less than a full rotation of the drill bit while delivering impacts to the drill bit with the hammer, so that the drill head deviates in the direction of the cutting action of the effective steering geometry.
Yet a further aspect of the invention provides a method for boring a hole through a medium using a horizontal drilling apparatus and steering a drill head of the drilling apparatus, comprising: pushing the drill head located at a front end of a drill string through a medium while delivering impacts to a drill bit located at a distal end of the drill head with a hammer driven by a liquid, wherein the drill bit includes an effective steering geometry suitable for steering the drill head and the drill head; periodically determining the angular orientation of the drill bit using a device for detecting angular orientation disposed on the drill head; and steering the drill head by: if boring through a compressible soil, changing direction during boring by pushing the drill string, so that the drill head deviates in the direction of an offset coupling member, which is offset from a center line of a longitudinal axis of the drill string without delivering impacts to the drill bit with the hammer and without rotating the drill string; or if boring through rock, delivering impacts to the drill bit with the hammer, so that the drill head deviates in the direction of the effective steering geometry.
Another aspect of the invention provides a horizontal directional drilling apparatus having a drill string adapted to bore through rock and compressible soil, the drilling apparatus having an aggressive flushing type hammer driven by a liquid, a method of operating an aggressive flushing type hammer, comprising: determining whether to active the aggressive flushing type hammer; if drilling in rock and the hammer is to be activated: reducing the liquid flow for driving the hammer to a first value substantially close to zero; applying a thrust force exceeding a predetermined threshold by a drive member of the drilling apparatus to the drill string and causing the hammer to shift out of a flushing position; and increasing the liquid flow to a predetermined threshold and continuing drilling in rock with the hammer activated; if drilling in compressible soil and the hammer is not to be activated: reducing the thrust force below a predetermined threshold while maintaining liquid pressure above a predetermined threshold on the hammer, thereby shifting the hammer into the flushing position; and continuing drilling in compressible soil without the hammer activated.
Yet another aspect of the invention provides a horizontal directional drilling apparatus having a drill string adapted to bore through rock and compressible soil, the drilling apparatus having a standard type hammer driven by a liquid, a method of operating a standard type hammer, comprising: determining whether to active the standard type hammer; if drilling in rock and the hammer is to be activated: Increasing the liquid flow to a value above a predetermined threshold; or increasing a thrust force generated by a drive member of the horizontal drilling apparatus to a value above a predetermined threshold; and continuing drilling in rock with the hammer activated; if drilling in compressible soil and the hammer is not to be activated: limiting the liquid flow to a value below a predetermined threshold required to activate the hammer; limiting the thrust force to a value below a predetermined threshold required to activate the hammer; and continuing drilling in compressible soil without the hammer activated.
Another aspect of the invention provides a system for use in horizontal directional drilling in compressible soil and rock, comprising: a horizontal directional drilling machine having a drill string coupled thereto, the directional drilling machine being used to rotate and push the drill string into a medium to be bored, the directional drilling machine including a drive member adapted to be coupled to a proximate end of the drill string and generally configured for applying a thrust force to the drill string; a pressure source for generating a working pressure to be transmitted through a liquid used for drilling; and a controller for controlling the thrust force generated by the drive member and for controlling the working pressure output of the pressure source; wherein the drill string includes at a distal end: a device for detecting angular orientation; a holder for the device for detecting angular orientation, the device for detecting angular orientation being disposed therein; a hammer driven by the liquid; and a drill bit; wherein, the holder, the hammer and the drill bit are connected head to tail along a longitudinal axis of the drill string with the holder being located at a proximate end of the drill head and the drill bit being located at a distal end of the drill head.
Another aspect of the invention provides a drill head for an apparatus for horizontal directional drilling, comprising: hammer driven by a liquid; and a drill bit driven by the hammer, the drill bit having an effective steering geometry.
Another aspect of the invention provides a drill head for an apparatus for horizontal directional drilling, comprising: a hammer driven by a liquid, the hammer arranged and configured to generate percussive blows; and a rotary bit assembly connected to the hammer, the rotary bit assembly arranged and configured for receiving the percussive blows, and having an effective steering geometry.
These aspects of the invention are described further in the detailed description that follows.